AJP - Renal Physiology, Vol 253, Issue 5 802-F809, Copyright © 1987 by American Physiological Society
Hormonal regulation of gluconeogenesis in cultured proximal tubular cells: role of cytosolic calcium
M. S. Goligorsky, D. Osborne, T. Howard, K. A. Hruska and I. E. Karl
Renal Division, Jewish Hospital of St. Louis, Missouri.
Gluconeogenic competence of primary cultures of canine renal proximal
tubular cells has been examined. Cells grown in 5 mM glucose media or in
glucose-free media exhibited pyruvate-stimulated glucose production, as
opposed to cells grown in 20 mM glucose media. By 72 h after the last media
change, confluent cells grown in 5 mM glucose medium turn from a
predominantly glycolytic to an oxidative type of metabolism. By this time,
glucose production exhibited pH, 3-mercaptopicolinate, and insulin
sensitivity. Parathyroid hormone, angiotensin II, and phenylephrine
stimulated glucose production in a nonadditive fashion. Single-cell
cystolic Ca2+ measurements using microspectrofluorometric techniques
revealed that all three hormones elicited Ca2+ transients in proximal
tubular cells. Ionomycin stimulated glucose production by proximal tubular
cells, suggesting that Ca2+ transients could represent a sufficient
stimulus for glucose production. When hormone-induced Ca2+ transients were
curtailed by a pretreatment with the membrane-permeant Ca2+ chelator,
Maptam, hormonal stimulation of glucose production was abolished,
suggesting that Ca2+ transients represent not only a sufficient, but a
necessary event in the stimulation of glucose production by these hormones.
